Lightmatter Connects Chiplets Optically

Lightmatter’s Passage substrate is an active photonic interposer for interconnecting chiplets. All the photonic components and supporting electrical circuits reside in a single multi-reticle piece of silicon.
Bryon Moyer
Bryon Moyer

Lightmatter’s photonic interconnect platform enables dense high-speed photonic links between processor chiplets for high-performance computing (HPC). Disclosed at Hot Chips, the Passage technology operates as an active photonic interposer, allowing high-bandwidth chiplet assemblies while abstracting away the photonic details. It’s a single piece of silicon spanning multiple reticles.

In its computing work, the company found that the interconnect between processors was a bottleneck impeding additional processor gains, so it turned its attention to balancing performance. By creating a silicon-photonics-based interposer, it makes those connections optically using silicon waveguides for higher bandwidth. Conversion between the electrical and optical domains occurs in the interposer, making it look like a standard electrical interposer. Passage has active components, however, allowing it to reroute connections during operation.

Lightmatter is a Boston-based startup whose primary focus has been photonic computing for HPC and AI. After launching the Envise computing platform, it completed an $80 million Series B funding round last year, bringing its total to $113 million.

Passage increases bandwidth—normally limited to 3.2Tbps per fiber array—to 768Tbps per chiplet site. Signals can route anywhere with a single hop, and 2ns maximum latency makes retiming unnecessary. The initial panel runs at 21W, less than 10% of a typical HPC chip’s power.

Lightmatter implements Passage designs on a custom basis; GlobalFoundries fabricates them. It may establish an off-the-shelf version, given market demand. The company withheld pricing.

Free Newsletter

Get the latest analysis of new developments in semiconductor market and research analysis.

Subscribers can view the full article in the TechInsights Platform.


You must be a subscriber to access the Manufacturing Analysis reports & services.

If you are not a subscriber, you should be! Enter your email below to contact us about access.

The authoritative information platform to the semiconductor industry.

Discover why TechInsights stands as the semiconductor industry's most trusted source for actionable, in-depth intelligence.